Objectives: There is considerable evidence that patients with carotid artery stenosis treated immediately after the ischaemic cerebrovascular event have a better clinical outcome than those who get delayed treatment. Biomechanical assessment of carotid plaques using high resolution magnetic resonance imaging (MRI) can help examine the relationship between the timing of carotid plaque symptomology and maximum simulated plaque stress concentration.
Methods: Fifty patients underwent high-resolution multisequence in vivo MRI of their carotid arteries. Acute symptomatic patients (n=25) underwent MRI within 72 hours of the onset of ischaemic cerebrovascular symptoms, whereas recently symptomatic patients (n=25) underwent MRI from 2 to 6 weeks after the onset of symptoms. Stress analysis was performed based on the geometry derived from in vivo MRI of the symptomatic carotid artery at the point of maximum stenosis. The peak stresses within the plaques of the two groups were compared.
Results: Patient demographics were comparable for both groups. All the patients in recently symptomatic group had severe carotid stenosis in contrast to acute symptomatic patients who had predominantly mild to moderate carotid stenosis. The simulated maximum stresses in acute symptomatic patients was significantly higher than in recently symptomatic patients [median (interquartile range): 313 x 10(4)dynes/cm2 (295-382) vs. 252 x 10(4)dynes/cm2 (236-311), p=0.02].
Conclusions: Patients have extremely unstable, high-risk plaques, with high stresses, immediately after an acute cerebrovascular event, even at lower degrees of carotid stenoses. Biomechanical stress analysis may help us refine our risk-stratification criteria for the management of patients with carotid artery disease in future.